Synthesis and properties of dithioacetals of conformationally constrained?-acyl-?-aminovinyl ketones of the 8-azasteroid

Synthesis and structure of 12-hydroxyimino derivatives of 16,16-dimethyl-8-aza-D-homogona-1,3,5(10), 13-tetraene-12,17a-dione

“…The strong bands at ν 1640-1630 cm -1 may be assigned in accord with our previous work [8,9] to stretching vibrations of C (17a) =O bond, while the bands appearing as shoulders may be assigned to C=N bond vibrations. The band of the N-OH group in 2 taken in a KBr pellet is found at ν 3180 cm -1 , while this band for a sample in chloroform solution is found ν 3580 cm -1 .…”

“…Ring B in the 2a-2b conformer pair has envelope conformation in conformers 2a and 2b; C (7) is the vent atom and has β-configuration. However, ring B in the 2c-2d conformer pair has chair or boat conformation, whose stern atoms, C (6) and C (9) have α-configuration.…”

“…Semiempirical AM1 and PM3 (Polak-Ribire algorithm) quantum-mechanical calculations of the molecular structure of 12-hydroxyimino derivative 2 show that this molecule exists as four conformers 2a-d differing in the conformation of rings B and C and the conformation of the unshared electron pair of N (8) relative to the proton at C (9) determining the fusion of rings B and C, which will arbitrarily be termed the α-configuration.…”

“…The long-wavelength band, according to our previous work [9], should be assigned to the trans-s-trans N (8) -C (14) =C (13) -C (17a) =O chromophore, while the short-wavelength band should be assigned to the aromatic chromophore (ring A).…”

“…The proton arrangement C (9) H-C (11) H 2 and C (6) H 2 -C (7) H 2 for conformers 2a and 2b are identical ( Fig. 2) and, as a result, a monotypic set of resonance signals corresponding to an ABX spin system for the C (9) H-C (11) H 2 protons and A 2 B 2 system for the vicinal C (6) H 2 -C (7) H 2 protons should be observed in the NMR spectra of these conformers.…”